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Sugar Factories Shutting Down!

Bruce Rinker
Bruce Rinker

Sugar factories are shutting down throughout the Roanoke region.  But this denouement is not due to any sad downturn in our regional economics.  Billions of years in the making, these are living factories that turn the power of the sun into sugars that fuel entire ecosystems.  It’s late autumn in the Valley, and that means that our oaks, maples, dogwoods, redbuds, and other deciduous trees are shutting down their chloroplasts for the cold winter months ahead.  The profligacy of summer yields to the starkness of a winter landscape.

Chloroplasts are nifty little packages in plant cells – 10 to 100 per cell – that make the leaves look green and produce a plant’s sugars in factory-like automation.  That’s about 500,000 chloroplasts per square millimeter!  If we consider the chloroplasts as the proverbial “black box” of science – or, more appropriately, the “green box” of life – these tiny organelles take in sunlight, carbon dioxide, and water to generate sugar with oxygen as a waste product.  At breath-taking speeds, thousands of chemical processes occur every second, day and night, inside these solar collectors to yield the sugars in sugar beets, sugar maples, sugar cane, and every other green plant on Earth.  Blessed be the chloroplasts!  All told, we estimate that this complex process makes 176 billion tons of sugars each year across the planet.  Imagine captured sunlight: when we eat our salads, we can almost taste the savory sweetness of a sunbeam!

In addition to all those sugars, other benefits to humans of this ancient process are staggering.  The U.S. Forest Service estimates that all the forests combined in the United States sequestered over 300 million tons of carbon per year from 1952 to 1992, offsetting 25% of the U.S. human-caused emissions of carbon in that period.  Further, over a 50-year lifetime, a tree generates $31,250 worth of oxygen, $62,000 worth of air pollution control, recycles $37,500 worth of water, and controls $31,250 worth of soil erosion.  Trees also remove other gaseous pollutants, making them living scrubbers especially in urban areas rife with human activity.

When autumn arrives, the chloroplasts shut down, sugar production grinds to a halt, and their unstable green pigments are absorbed by the plant.  Suddenly, other pigments – present all along – show up in ever-intensifying palettes of foliage across our mountain landscapes.  The trigger for such deep splashes is a combination of dry sunny days followed by cool dry nights.  Such vibrant panoramas are fodder for the poet and the romantic in us all – and a multi-billion-dollar boon to the tourist industry.

But this rainbow is not designed for our enjoyment.  It may be related to tree survival.  Some experts think that these wild colors – all those fiery reds, oranges, and yellows – may be warning signals to insects in search of winter homes.  A red-pigmented leaf, for example, may suggest a healthy tree with enough energy to fill future leaves with unappetizing plant toxins.  So, madam aphid or mister beetle, keep moving or you’ll regret your nibbles here!

You’ve probably guessed that this alchemy of converting sunlight into sugar is called photosynthesis, a descriptive term coined by English scientist Charles Barnes in 1893.  Photosynthesis is an old, complex, and awe-inspiring course of action also found among algae and some bacteria.  It’s one of those ecological processes that distinguish Earth from all other known planets.  It’s a never-ending dance between energy and life, like the great Lord Nataraja in Hindu spirituality: an exaltation of conversion to inspire the ages.

H. Bruce Rinker, Ph.D.
Science Department Chairman
[email protected]

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